1. Field of the invention
The present invention relates to a magnetic recording medium, for example, a magnetic tape, a magnetic disc, etc., and particularly to a magnetic recording medium having perpedicular magnetic anisotropy.
2. Description of the prior art
Recently in the field of magnetic recording medium, perpendicular magnetic recording system was proposed as a new system that would enable recording of exceedingly high density compared with the currently prevailing longtitudinal recording system and the researches and developments of such new system are now intensively proceeded.
In order to realize the perpendicular magnetic recording, a medium having an easy axis of magnetization in the direction perpendicular to the surface of the medium is required.
Up to this date, some magnetic films are known to have such magnetic property as above. They are, for example alloys produced by a sputtering method or a vacuum deposition method to have such combinations of the components as Co-Cr, Co-Ti, Co-V, Co-Mo, Co-W, Co-Mn or Co-Ru, as described in the Journal of Applied Magnetics Society of Japan, Vol. 8, No. 1 (1984), page 17.
For example, Co-Cr recording films with perpendicualar magnetic anisotropy are reported by S. Iwasaki, et al. in the IEEE Transacctions on Magnetics, Vol. MAG-14, No. 5 (1978), pages 849-851.
These known perpendicular magnetic mediums include Co as one of the main components, but the use of Co causes some problems about costs and the stability of supply.
There are some reports on perpedicular magnetic films including relatively cheap Fe as one of the main components in place of Co.
For example, Fe.sub.1-x Cr.sub.x (x=0.33-0.40) films are reported by K. Saiki, et al. in the Journal of Applied Magnetics Society of Japan Vol. 9, No. 2 (1985), pages 61-64; Fe.sub.1-x Nd.sub.x (x=0.40-0.45) films are reported by T. Suzuki in the Japanese Journal of Applied Physics, Vol. 24, No. 3 (1985), pages L199-202; and Fe.sub.61.5 Nd.sub.34 Ti.sub.4.5 film is reported by K. Tsutsumi, et al. in the Japanese Journal of Applied Physics, Vol 23, No. 3 (1984), pages L169-L 171.
These Fe-containing films however still including large amounts of precious metals such as Cr or Nd and so their production costs are still high.